Drag & Drop in Navigator 4: Bringing Drag Element to Top

Drag & Drop in Navigator 4:keeping the dragged element on top

We have avoided discussing the z-index property of positioned
elements in our columns so far, and guess what? We're not going to
discuss it this time either.

Instead, for simplicity's sake, we will create a variable activeEl,
which will store the element that is currently on top of other
elements. The last line in our code should be...

activeEl = document.elDRAGFour

...if elDRAGFour hides other elements upon page load, or if it is already
on top by virtue of its being defined last, or just because we want it
to be considered the top element.

In grabEl, we check to see if the element-to-be-dragged is on top.
That is, if it is activeEl. If it isn't we use the JavaScript 1.2 method
moveAbove(), which takes one argument: the element we should move above.
Once our element is above activeEl, it itself is assigned to activeEl,
for the next time an element is dragged.